When a web material is continuously fed from a plurality of successive rolls, the ends of the rolls may be spliced together to eliminate interruption to the web feed. Different types of splices can be formed, including a lap splice, a butt splice, and a gap splice. A lap splice is formed when a portion of an expiring web overlies a portion of a web from a new roll with the under surface of the overlapped portion of the one of the webs adhering to the upper surface of the other web. With a butt splice, the trailing end of the expiring web is in intimate contact with the leading end of the new web, but no overlap exists. A gap splice is formed when no overlap exists and the ends of the expiring web and new web are separated. For the butt splice and the gap splice, tape may be employed to connect the ends. U.S. Pat. No. 5,277,731 relates to the formation of a butt splice. U.S. Pat. No. 4,652,329 and U.S. Pat. No. 5,045,134 teach apparatus and methods for forming a splice.
The quality of the splice formed may affect subsequent processing of the web material. For example, if the web material is to be further processed, such as by the addition of a layer or coating, the quality of the splice may affect how the web material tracks or steers through the web handling equipment during the processing. The quality of the splice may also indicate when adjustments are needed to the splicing equipment and may provide an indication of impending mechanical problems with the splicing equipment. Thus, monitoring of the quality of the splice may be advantageous. Skew and offset are two characteristics which can be measured to provide an indication of web alignment at a splice.
NASA Tech Briefs, December 1996, page 104, relates to a gauge for measuring mismatch and peaking at welds. A hand-held tool is pressed against the weld bead to provide a measurement of the mismatch and peaking at a weld joint between two flat plates. While such apparatus may have achieved certain degrees of success in its particular application, the apparatus is not suited for flexible web material, particularly thin web material which is light sensitive. For example, contact of the gauge with photosensitive web material may cause scratches or abrasions. Further, the apparatus operates off-line, so would interrupt the manufacturing process.
U.S. Pat. No. 5,271,284 relates to a lap splice width monitor which senses the leading and trailing edge of a lateral splice and produces an indication of whether the total splice width is within a dimensional criteria. Such an apparatus, utilized in discrete processing, does not provide a measurement of the characteristics of a formed splice, for example, skew and offset.
U.S. Pat. No. 4,297,585 relates to a system for the detection of splicing defects in film. The system is directed toward detecting defects causes by improperly located splices and improperly sized gaps between adjacent film strips. While such a system may detect defects, the system does not provide a quality of the splice whereby a measure of web alignment is obtained.
Accordingly, there exists a need for an apparatus and method which provides for the measurement of web alignment at a splice, for example, skew and offset. There is a further need for such an apparatus and method which provides for the measurement of characteristics of a splice on-line, so that the web feed does not need to be interrupted and since the tension applied during transport may affect the characteristics of the splice. Further, such apparatus and method should be suited for high speed transport applications, and for flexible web material, such as photosensitive film or paper. Still further, the measurements should be able to be made without physical contact with the web material.